A wide variety of medical procedures require infusion of a fluid into a patient. For example, vascular imaging technologies may require use of a contrast media that is injected into the patient. More specifically, computed tomography (CT) is an imaging technology that utilizes a contrast media and may be employed for the noninvasive evaluation and assessment of a vascular system (i.e., CT angiography or CTA). Multidetector computed tomography (MDCT) is one specific type of CT that may be utilized for CTA. For proper imaging of a vascular system via CT, intravenous contrast media injection protocols are coordinated and selected for the anatomic area of interest.
More particularly, conventionally, a so-called “power injector” system may be employed for injecting contrast media at a high pressure into a peripherally inserted intravenous (IV) line. For example, such power injectors or injection systems may be commercially available from Medrad, Inc., a subsidiary of Schering AG, Germany and may be marketed as STELLANT® injection systems. Because CT procedures are often defined in terms of a desired flow rate of contrast media, such power injection systems are, in general, controllable by selecting a desired flow rate. Accordingly, such power injection systems may develop pressure (within the maximum pressure capability of the power injection system) as is necessary to maintain the selected flow rate. Accordingly, as may be appreciated, obstructions in the IV lines or use of IV lines that are not structured to withstand the pressures of a desired injection rate may cause the power injector to generate a pressure that exceeds a suitable pressure limit for the IV line. After intravenous injection, a bolus of contrast material, may flow within the vascular system of the patient to the right side of the heart, through the lungs, into the left side of the heart, and through the remaining circulatory system. After the bolus of contrast media is injected into the patient, portions of the contrast media may remain in the right side of the heart. Thus, the overall effectiveness of contrast enhancement may depend on a multitude of factors. For example, a patient's characteristics (e.g., body size; circulation, including cardiac output and circulating volume, and renal function), the contrast characteristics (e.g., volume, injection rate, iodine concentration, etc.), and the CT technique (e.g., access and route of administration, scan delay, scan speed, and injection pattern) may each influence the overall degree of contrast enhancement.
By way of background, conventionally, relatively long scan times have been accompanied by relatively long contrast media delivery times. However, because scan times continue to decrease, relatively fast delivery of contrast media may be desired. Explaining further, in coronary CTA, a large enough volume of contrast material must be administered at a sufficiently high rate to reach and maintain a suitable concentration throughout a selected scan time (e.g., a 15 second scan time), and within a selected region of the anatomy (e.g., an axial scan distance of 20 cm, which may include the left ventricle and outflow tract). It also may be desirable that contrast density values are sufficient to facilitate the segmentation techniques used in multidimensional post-processing. A typical contrast media used in coronary CTA may have an iodine density of about 300 milligrams per milliliter to about 350 milligrams per milliliter. Also, since contrast media may be radioactive, reducing the overall quantity of contrast media required to perform an imaging process may be advantageous.
The pressure required for contrast injection depends on many factors, including flow rate, contrast viscosity, configuration of infusion tubing, such as tube diameter and length, and any obstruction or restriction to flow (e.g., kinks, curves, fittings, compression). As mentioned above, to maintain the flow rate required for a CT or Mill study, a power injector may generate high pressures. Ruptures can occur when the injection pressure exceeds the tolerance of the vascular access device(s). Other problems may occur due to timing errors between the scan and the contrast. In order to maximize the rapid scanning capacity of the newer vascular imaging devices, the starting of the scanning process can be delayed a predetermined amount of time after injection of the contrast media has begun. If the scan starts too early, just as the contrast is arriving at the heart, arteries can appear smaller than they really are when the image is post-processed. On the other hand, if scanning is delayed too long, image artifacts can arise from diluted contrast in the cardiac veins. The window of opportunity for optimal scans may be very small, because contrast media circulates quickly through cardiac arteries and into cardiac veins.
Some diagnostic or medical procedures may advantageously employ a subcutaneous vascular access port for introducing a fluid into the vasculature of a patient. Access portals, or ports, provide a convenient method to repeatedly deliver medicants to remote areas of the body without utilizing surgical procedures. The port is implantable within the body, and permits the infusion of medications, parenteral solutions, blood products, contrast media, or other fluids. Additionally, the port may be used to aspirate blood from the patient. Such access ports typically include a cannula-impenetrable housing which encloses one or more fluid cavities or reservoirs and defines for each such fluid cavity an access aperture communicating through the housing. A cannula-penetrable septum is positioned adjacent to and seals each access aperture. An outlet stem communicates with one or more of the fluid cavities for dispensing medication therefrom to a predetermined location in the body of the patient through an implanted catheter attached to the access port. Once the access port and the catheter have been implanted beneath the skin of a patient, quantities of fluid, such as medication, blood, etc., may be dispensed through one such fluid cavity by, for example, a cannula (e.g., a needle), passed through the skin of the patient and penetrating the septum into one of the respective fluid cavities. This medication is directed through the distal end of the catheter to an entry point into the venous system of the body of the patient. Further, blood may be aspirated through the subcutaneous access port. Thus, use of an access port may allow for vascular access without needle sticks into the vasculature of a patient.
However, conventional access ports and attendant infusion systems have not been suitable for performing power injection.
Particularly, the use of power injection systems in combination with conventional vascular access ports has achieved less than ideal results. Thus, it may be appreciated that vascular access ports for infusion systems and infusion-related apparatuses structured for performing power injection may be advantageous.